The present invention relates to the field of spectacles and more particularly to hinges for spectacle frames.
More particularly, the present invention relates to an elastic hinge, particularly for spectacle frames, comprising two hinge elements rotatably mounted around a pivot, a cam profile integral with the first hinge element, a bearing piece movably mounted in the second hinge element along an elastic translation axis, having a first contact area for co-operating elastically with the cam profile and for giving the hinge at least one stable position, and a lock for the hinge when a position of excessive opening is reached.
The present invention particularly relates, in a hinge of the aforementioned type, to improvements of the lock for the hinge when a position of excessive opening is reached.
It is conventional to produce spectacle frame hinges having two stable positions owing to a bearing piece co-operating elastically with a cam profile. One stable position of the hinge corresponds to the closed position and the other corresponds to the open position of the arms of the frames. It is also conventional to provide a lock for the hinge when a so-called position of excessive opening is reached. The position of excessive opening corresponds to the open position of the spectacle arms to which an additional angle of opening, or angle of excessive opening, is added.
FIGS. 1, 2, 3 and 4 represent various conventional, elastic hinges equipped with a stop against excessive opening.
The hinge 10 represented in FIG. 1, described by European Patent EP 992,831, comprises two hinge elements 20, 30, a pivot 15 passing through the two hinge elements, a ball 31 slidably mounted in a cylindrical cavity 32 made in the second hinge element, and a cam profile 21 made at the proximal end of the first hinge element. A coil spring 33 arranged in the cavity 32 pushes the ball 31 against the cam profile 21. The latter has two hollows 21-1, 21-2 separated by a bump 21-3 for respectively giving a stable closed position and a stable open position to the hinge. The cam profile also comprises an protrusion 21-4 which, when the hinge is opened in excess of the position defined by the hollow 21-2, pushes the ball into the cavity 32 until it reaches a rear translation stop. The rear translation stop is here obtained by a reduction in the diameter of the cylindrical cavity, forming a shoulder preventing the ball from entering the lower part of the cavity where the spring is located. Another way of obtaining a rear translation stop involves ensuring that the spring reaches a state of maximum compression locking the translation of the ball in the cavity (so-called joined coil stop). As the ball 31 is locked, the protrusion 214 of the cam profile finds itself locked against the ball and the hinge cannot open in excess of the position of excessive opening thus determined.
The hinge 11 represented in FIG. 2, described by European Patent EP 889,347, comprises the aforementioned elements, designated by the same reference numerals. Thus, two hinge elements 20,30, a pivot 15, a ball 31 slidably mounted in a cavity 32 made in the second hinge element 30, a coil spring 33 and a cam profile 21 made on the first hinge element 20 can be seen. The cam profile also comprises two hollows 21-1, 21-2 separated by a bump 21-3 for obtaining the two aforementioned stable positions. The outer envelope of the second hinge element comprises two lips 34,35 between which the cam profile 21 is arranged (only the lip 34 being visible in FIG. 2). The outer envelope of the first hinge element comprises a V-shaped shoulder 22 arranged opposite the end of the lip 34. The locking of the hinge in position of excessive opening is here obtained by the fact that the end of the lip 34 comes up against a wing 22-1 of the shoulder 22, as can be seen in the FIG. 2.
The hinge 12 represented in FIG. 3, described by European Patent EP 266,307, comprises the aforementioned elements, designated by the same reference numerals. The locking of the hinge in a position of excessive opening is here obtained by the fact that the envelope of the first hinge element 20 comprises a protrusion 23 that co-operates with a cavity 36 provided in the second hinge element 30. The end of the protrusion 23 is flat and comes up against a flat wall that is at the bottom of the cavity 36 when the position of excessive opening is reached.
The hinge 13 represented in FIG. 4, described by International patent application publication WO 01/179917, comprises two hinge elements 20, 30, a pivot 15, a flat-top piston 37 slidably mounted in a cavity 32 made in the second hinge element 30, and a cam profile 24 provided at the proximal end of the first hinge element 20. A coil spring 33 arranged in the cavity 32 pushes the piston 37 against the cam profile 24. The latter has two flat sides 24-1, 24-2 co-operating with the flat top of the piston for obtaining the two aforementioned stable positions, and a fillet 24-3. In a position of excessive opening, the fillet 24-3 locks itself against the top of the piston 37, which finds itself in rear translation stop position. The rear translation stop is here obtained by the fact that a lower side 37-1 of the piston top comes up against a corresponding inner side 30-1 of the hinge element 30.
After all is said and done, two types of stops against excessive opening can be distinguished in previous practices.
The stops of the first type, or so-called axial stops, are implemented in the hinges represented in FIGS. 1 and 4. They involve locking the cam/bearing piece system, the bearing piece being a ball or a piston, and require providing a rear translation stop to lock the bearing piece.
The stops of the second type, or socalled radial stops, use specific contact surfaces provided on the outer envelopes of the hinge elements, as is the case in the hinges represented in FIGS. 2 and 3. In this case, the cam/bearing piece system only ensures the two stable positions are obtained and is not involved in locking the hinge.
The disadvantage of axial stops is that in a position of excessive opening, the areas of the bearing piece and the cam profile that are in contact are quite small. A high pressure is thus exerted on the contact areas when the user attempts to pull the arm of the spectacles beyond the position of excessive opening. This high pressure is likely to damage the cam profile.
Conversely, radial stops enable two flat surfaces to be put in contact, as can be seen in FIGS. 2 and 3, hence a better distribution of the excessive opening force and a weaker pressure exerted on the surfaces in contact. Furthermore, the excessive opening stress is not exerted on the contact areas of the bearing piece and of the cam profile. On the other hand, radial stops have a disadvantage in terms of style, due to the fact that the surfaces forming the stop are visible on the hinge elements and difficult to conceal. Radial stops therefore restrict the possibilities of designing hinges whose outer appearance is smooth and aesthetically pleasing, which constitutes a disadvantage in the field of spectacles in which style is of utmost importance.